1. Field of the Invention
The invention relates to methods and apparatus for providing security for digital data stored on data storage media such as magnetic and optical disks and tapes.
2. Description of the Related Art
Over the past several years, personal computing systems have become more powerful, smaller, and less expensive. As this has occurred, more and more computing applications are performed on personal computer platforms. Local and wide area networks of personal computers are now often used in corporate and business applications instead of the large mainframes used for the same applications in the past. A further result of the increases in performance and decreases in price of personal computers is a dramatic increase in personal computer use for household financial and other sensitive and preferably confidential information.
The use of personal computers in these applications raises data security and privacy issues which have thus far been insufficiently resolved. Laptop and other personal computers, as well as the removable data storage media used in them are transported, mislaid, lost, and sometimes stolen. Consequently, security and privacy issues which were not present when computers and their data storage media were generally fixed have now become prominent. Administrators of computer resources in the business environment must remain aware of the location of portable computing devices as well as the nature of the programs and data stored on them. For home users, concerns arise if credit card, social security, or bank account numbers are present on fixed or removable media which may be lost or stolen.
To resolve a few of these concerns, some programs allow the user to password protect documents or files, thereby preventing access to the data in the file unless the password is known. This provides limited security, however, since these schemes are easy to defeat with widely available password extraction programs. Furthermore, although the act of opening the file may be restricted in the relevant application program, the data itself resides on the media in raw form, and may still be extracted by a trained computer user.
Systems have also been proposed which perform encryption on data and application programs stored on tape and disk. These systems provide improved security over the password protection described above. As one example, a system disclosed in U.S. Pat. No. 5,325,430 to Smyth et al. (incorporated herein by reference in its entirety) includes a security module attached to a personal computer which performs data and application program encryption. The security module communicates with a removable smart card assigned to a given user which contains encryption keys used by the security module. Although the security provided by this system is adequate for many applications, the circuitry used to implement the system is complex, and administration of the system for producing and assigning keys and smart cards is time consuming and expensive.
Another system for encrypting files is disclosed in U.S. Pat. No. 5,235,641 to Nozawa et al., the disclosure of which is also incorporated herein by reference in its entirety. In this system, data stored to a magnetic tape is encrypted by a cryptographic adapter which is located in the data path between a host processor and a tape drive. In this system, the host processor generates cryptographic keys which are stored on the tape itself. This requires additional logic to encrypt the keys as well as the data, and consequently, this system requires relatively complex circuitry, and leaves the key potentially recoverable from the tape itself if the key encryption scheme is broken.
Thus, existing encryption systems for personal and portable computers have serious drawbacks, and have not been widely implemented. In particular, a system which is useful for an individual personal computer user has not been heretofore provided. Such a system should provide data security with flexibility and without expensive administration or implementation.